Change integral bounds

[MassimoCimmino]

Integrals are evaluated one time step at a time, using the same numpy.inf upper bound for every time step. The evaluation of integral can be made more efficient by using the property:
integral(f(x), x=a..c) = integral(f(x), x=a..b) + integral(f(x), x=b..c)

As an example:

pygfunction/pygfunction/heat_transfer.py

Lines 399 to 402 in 79e0198

	h = np.stack(
	[0.5 / H2 * quad_vec(f, 1.0 / np.sqrt(4.0*alpha*t), np.inf)[0]
	for t in time],
	axis=-1)

Becomes:

a = [1.0 / np.sqrt(4.0*alpha*t) for t in time]
b = [np.inf] + a[:-1]
h = np.cumsum(np.stack(
    [0.5 / H2 * quad_vec(f, a[i], b[i])[0]
     for i, t in enumerate(time)],
     axis=-1), axis=-1)

[MassimoCimmino]

'equivalent' solver

Rectangular fields

Field of 100 boreholes with two different lengths

[MassimoCimmino]

'similarities' solver

Rectangular fields

Field of 100 boreholes with two different lengths

[MassimoCimmino]

'detailed' solver

Rectangular fields

Field of 100 boreholes with two different lengths

(nSegments=64 is from the 'similarities' solver)